When a vehicle having a rotating electric machine is traveling at a high altitude, the insulating properties of the rotating electric machine and a power supply circuit, operating with a high voltage, are degraded due to a drop in the atmospheric pressure. In such situation, a boosting voltage supplied to the rotating electric machine may be limited. In order to limit the boosting voltage, an atmospheric pressure sensor is used as means for detecting the atmospheric pressure. The atmospheric pressure sensor is monitored for abnormalities, because if an abnormality is caused in the atmospheric pressure sensor, the boosting voltage will not be controlled accurately.
For example, JP 2004-166341 A discloses an abnormality detection device for pressure sensors, in which abnormalities in an intake pressure sensor and an atmospheric pressure sensor, which are two pressure sensors involved in engine operation, are detected based on presence or absence of a deviation between the detection values of the two pressure sensors at the time when the engine has not been started before cranking-up so that the detection values of the two pressure sensors must be almost the same.
As described in JP 2004-166341 A, if abnormalities in the atmospheric pressure sensor are detected using the intake pressure sensor of the engine, there is no need to provide a particular sensor for monitoring abnormalities in the atmospheric pressure sensor. In order to determine abnormalities in the atmospheric pressure sensor using the intake pressure sensor of the engine, JP 2004-166341 A describes that a feature that an intake pressure of the engine returns to the atmospheric pressure when the engine stops is utilized. This means that abnormalities in the atmospheric pressure sensor can be detected by the intake pressure sensor only when the engine has stopped. Therefore, in some cases, the vehicle may travel for a long time without having an opportunity to detect abnormalities in the atmospheric pressure sensor.